What is FTP and how do I use it?

One acronym in cycling is both widely used and often misunderstood: FTP (Functional Threshold Power).

What is FTP? And what does it mean? Finally, and most importantly: how do you improve and use FTP for your specific training and racing goals?

What is FTP in cycling?

FTP, or Functional Threshold Power, is the maximum average power in watts that – at least theoretically – a cyclist can sustain for more or less an hour. We say theoretically because the tests to calculate FTP are often shorter than an hour (20, 30 or 40 mins) and they use the highest average power of those values to calculate the 60 min one.

From a physiological point of view, if we looked inside our muscles, FTP would approximately correspond to our Lactate Threshold, the point where lactate accumulates exponentially in our muscles and eventually stops us from pushing power through the pedals. 

However, it's worth mentioning that FTP (which more or less corresponds to the Anaerobic Threshold, or Lactate Threshold, or Maximum Lactate Steady State) is a blurred line and not a fixed value. So there's always wiggle room to remember once you’ve performed the test. Furthermore, FTP values can differ quite a lot from one day to another, indoors vs outdoors, if you don't calibrate your power meter, and if the conditions you perform in change. So, don’t get disappointed if one day you don’t score the numbers you had wished for.

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Tools you need to calculate FTP

To calculate your FTP, you need a power meter, a tool that measures the torque in newton metres and the power in watts you apply to your pedals, cranks or hubs. "A power meter provides a training metric based on physics," explains Chris Meyer, Exercise Physiologist and Master Coach for the Peaks Coaching Group. "And power data provides real-time actionable data to improve the consistency of a workout, post-workout analysis, and also helps to pinpoint your strengths and weaknesses. I recommend training with power to any athlete who wants to improve their training program." 

How to test for your FTP

Ideally, the most accurate way to calculate FTP would be riding as hard as possible for an hour (The Hour of Power test), but that is often a daunting task for many. Therefore, the most used and common ways to calculate FTP are often the 20 or 30-min tests.

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If you decide to use the 20-min test to calculate your FTP, the most important thing is to be consistent with how you benchmark your fitness over time. If you do it indoors on a turbo trainer (or a smart trainer with built-in power meter), then keep testing indoors, and make sure your power meter is updated, charged and calibrated. And don't forget to use the same set-up over time and perform at the same time of the day, following similar training days prior.

On the other hand, if you perform the test outdoors, make sure the road where you do it is quiet and ideally has a 2-4% gradient. In this scenario, you would be engaging more muscles (especially the big ones of the glutes and quads), and you will get better results.  

Before the 20 minute test, it's essential to do a good warm-up, such as 10-15 mins of easy pedalling, where you can also fit in some higher intensity efforts to get ready to push (eg. 4 x 30 sec hard, 30 sec easy). After the warm-up, the test is pretty straightforward: you need to push as hard as possible for those 20 minutes, but ideally you should push a constant output, not going too hard at the beginning and then blow up at the end. It's a stern test, but you'll learn to suffer and how to perform it with time. And don't forget to cool down for 10-15 minutes at the end.

How to calculate your FTP

When you complete the test, using your bike computer or one the various fitness apps on the market (Training Peaks, Garmin Connect, Strava for example), extrapolate the maximum average power output for those 20 minutes.

To calculate your FTP, multiply the average power by 0.95 and you'll get your value, or the prediction of the power you should be able to sustain over an hour. Your 60 min FTP is then calculated as the 95% of your 20min one, but some coaches suggest multiplying the 20min one by 0.90 to have more reliable values over time.  

How using FTP can improve your fitness

"Training with FTP allows you to pace your efforts better for racing, time trialling, intervals, climbing, and so on," explains Meyer. "Knowing your FTP will also inform you how hard you can go without blowing up."

Using power over (or in conjunction with) other metrics will also make your training and pacing more precise. Using power, you can target the metabolic pathways that you need to train to improve your cycling fitness with greater granularity. And these are pretty different if you're a track cyclist or an endurance rider.

Through FTP you can precisely calculate your training zones, which are power ranges that target those specific metabolic adaptations. Many coaches and third party apps like Zwift, TrainerRoad and Wahoo SYSTM use percentages of FTP to structure training sessions. 

"A power meter provides a training metric based on physics," explains Meyer. "And power data provides real-time actionable data to improve the consistency of a workout and data for post-workout analysis but also helps you to pinpoint your strengths and weaknesses. I recommend training with power to any athlete who wants to improve their training program." 

How to improve your FTP

There are several ways you can improve your FTP. One of the most straightforward is to ride intervals at (or above) your FTP values, followed by rest intervals. For example:

10 mins warm up
10 x (2 min @FTP, 2 min easy)
10 mins cool down 

Week after week, you can increase the time you spend at FTP, and decrease the rest intervals. Another way, maybe one that's more counterintuitive, is to ride more, but at lower intensities. Riding longer in the easy training zones is actually the best way to improve your endurance and your upper-end thresholds at the same time.

What are the limitations of FTP? 

Of course, metrics and tools have their limitations. For example, using FTP to benchmark your fitness programme requires a power meter, which can be expensive. "Power meter prices range from $250 - $1500," says Meyer. "And the price comes down to the features [and level of accuracy] you want."

Furthermore, FTP does not have the same level of accuracy that metabolic or lab tests have. For example, FTP gives you a functional power number representing your threshold, but it doesn't tell you how many of those watts come from your aerobic (which uses oxygen and fat as main fuel sources) or anaerobic pathways (which uses carbs primarily as fuel sources).

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And as we have already highlighted, to extrapolate the 60min max power from a 20min test is already a limitation in itself, particularly if your focus is long endurance sportives and Gran Fondos, and not criterium races (which are short and sharp).

Nevertheless, within its intrinsic limitations, it can still be used successfully, as it has been by many professionals and amateurs alike. And if you have never used it before, it will certainly give a positive boost to the way you train.